System and Method for Load Balancing in Knee Replacement Procedures

ABSTRACT

The present disclosure relates to a system and method of knee ligament balancing for knee replacement procedures. The disclosure provides a system of components to implant to achieve ligament balancing. In addition, instruments and methods are provided to achieve the desired balance of the ligaments before final fixation.

The present application is a continuation of U.S. patent applicationSer. No. 14/816,939, filed Aug. 3, 2015, now U.S. patent Ser. No.______, which claims priority to and the benefit of U.S. ProvisionalPatent Application No. 62/032,458, filed Aug. 1, 2014, each of which ishereby incorporated by reference in its entirety.

BACKGROUND

Knee ligament balancing is necessary for long term successful total kneefunction. Valgus and varus knee arthritis is associated with variabledegrees of ligament contracture on the worn side and attenuation orlaxity of the ligaments on the opposite compartment. If not addressedeither limb mal-alignment or knee instability is expected. Thereforeligament lengthening or release should be performed in most total kneeprocedures. Problems with ligament imbalance are known to lead toaccelerated poly wear, pain instability and stiffness.

Currently no consensus exists regarding the best method to produce abalanced knee. Many differing techniques and sequences for ligamentrelease have been reported over the years. New tools have beenintroduced to help the surgeon; for example, computer-assisted surgeryand tensor balancers. However, randomized control trials comparingdifferent techniques, sequences, and tools are limited. The best methodof achieving the balanced knee is yet to be determined.

In one example of an arthritic knee, the worn lateral side has a tightcollateral ligament while the superficial medial collateral ligament onthe less worn side is too loose. With reference to FIG. 1, in additionto any cartilage damage on the condyles, the knee is misaligned suchthat the lateral ligament LL is too short or tight, while medialligament ML is too long or lax to properly maintain the alignment of theknee. As shown, the joint 10 between the femur F and the tibia T ismisaligned.

Referring to FIG. 2, the knee joint of FIG. 1 is illustrated withprosthetic knee components 12 and 14 positioned in the joint. Utilizinga prior art technique, pie cuts 16 are made in the lateral ligament LLto lengthen the ligament to attempt to achieve re-alignment of the kneejoint. However, as shown this technique does not address the laxity ofmedial ligament ML. Moreover, the cuts in the LL ligament tend to weakenthe ligament which may lead to rupture.

Referring to FIGS. 3A-3C, a technique is illustrated for shortening themedial ligament ML by cutting out a bone block 20 with attachedligament, removing cancellous bone with instrument 24, and recessing themedial collateral ligament origin into the metaphyseal bone opening 22of the femur. The bone block 20 may be held in place by suture 26extending through the femur.

Methods of knee ligament balancing are still controversial and thereremains a need for improvement devices and methods for obtaining abalanced knee.

SUMMARY

In one aspect, the present disclosure provides a system for loadbalancing in knee replacement procedures. The system comprises aligament release portion including an epicondylar osteotomy fixationguide and an epicondylar osteotomy fixation member, along with aligament tension portion including an elongated ligament tension elementhaving a first anchoring element disposed near an inferior end andconfigured for anchoring below the knee joint, and a femoral anchoringportion for movably anchoring the elongated ligament tension element tothe femur.

In another aspect, the present disclosure provides a method for loadbalancing in knee replacement procedures. The method comprisesevaluating ligament balance in a knee and loosening a first over tightligament on a first side of the knee by performing a partial epicondylarosteotomy adjacent a bone/ligament attachment point of the firstligament by severing a superior portion of the bone adjacent thebone/ligament attachment point while leaving an inferior portion of thebone adjacent the bone/ligament attachment point connected to the nativeepicondylar bone to thereby form a bone flap positioned over a bonedefect. The method includes adjusting the tension on the first ligamentby effectively lengthening the first ligament by moving thebone/ligament attachment point on the bone flap inferiorly toward thefoot; and fixing the bone flap with interconnected bone/ligamentattachment point to the epicondyle to maintain the position of the boneflap relative to the epicondyle to thereby fix the new effective lengthof the first ligament.

In yet a further aspect, the present disclosure provides a method forload balancing in knee replacement procedures. The method comprisesevaluating ligament balance in a knee and identifying a loose ligamentthat is too lax to properly function to support the knee after insertionof a knee replacement device. The method further includes anchoring aninferior end portion of an elongate ligament support member below theknee, extending the elongate ligament support member along the looseligament, evaluating tension of the elongate ligament support member inat least one of flexion and extension of the knee to determine theappropriate tension on the elongate ligament support member, and fixinga superior portion of the elongate ligament support member to the femurto maintain the appropriate tension.

In yet a further aspect, the present disclosure provides a knee loadbalancing instrument. The balancing instrument comprises a first bellowshaving a first upper bone engaging end plate and a first lower boneengaging endplate and a first movable sidewall joining the first upperand lower bone engaging plates along a longitudinal axis, the firstmovable sidewall formed of corrugated material inhibiting outwardexpansion and permitting longitudinal expansion, the first upper andlower bone engaging plates along with the first movable sidewall joinedto form a fluid tight first fluid chamber. The instrument preferablyalso includes a second bellows having a second upper bone engage endplate and a second lower bone engaging endplate and a second movablesidewall joining the second upper and lower bone engaging plates alongthe longitudinal axis, the second movable sidewall formed of corrugatedmaterial inhibiting outward expansion and permitting longitudinalexpansion, the second upper and lower bone engaging plates along withthe second movable sidewall joined to form a fluid tight second fluidchamber. The instrument includes a first tube joined to the first fluidchamber and configured for connection a first pump; and a second tubejoined to the second fluid chamber and configured for connection asecond pump, wherein the first fluid chamber and associated firstmovable sidewall is movable longitudinally independently from the secondfluid chamber and second movable sidewall.

These and other aspects of the present disclosure will be apparent fromthe following disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a front view of a knee with improper alignment andligament balance.

FIG. 2 illustrates the knee of FIG. 1 with knee replacement deviceinserted and a prior art technique utilized to lengthen the shortenedligament on the lateral side.

FIGS. 3A-3C illustrate the knee of FIG. 1 with a knee replacement deviceinserted and a prior art technique being employed to shorten the laxligament on the medial side.

FIGS. 4A-4C illustrate a knee being prepared to receive a kneereplacement device and a new technique according to the presentdisclosure for lengthening the ligament on the shortened side.

FIGS. 5A-5C are various views of an epicondylar drill guide.

FIG. 6 illustrates the drill guide of FIGS. 5A-5C positioned in anepicondylar defect of the knee illustrated in FIG. 4C.

FIG. 7 illustrates the knee of FIG. 4 with a screw inserted to maintainthe position of the partial epicondylar osteotomy bone flap.

FIG. 8 illustrates a further fixation device suitable for fixing thepartial epicondylar osteotomy bone flap.

FIG. 9A illustrates an elongate ligament replacement positioned betweenthe femur and tibia in flexion.

FIG. 9B illustrates an elongate ligament replacement positioned betweenthe femur and tibia in extension.

FIG. 10 illustrates a drill guide associated with a femor component of aknee replacement device positioned in the knee joint.

FIG. 11 illustrates a knee with a knee replacement device positioned inthe joint, the knee being misaligned and the medial ligament being lax.

FIG. 12 illustrates the knee of FIG. 11 with the implementation of theligament tightening system and method to bring the knee into alignment.

FIG. 13 illustrates an elongate ligament replacement for use in oneembodiment of the present disclosure.

FIGS. 14A and 14B illustrate the top and bottom, respectively, of a kneebellows system.

FIG. 15A is a cross-section of FIG. 14A taken along line A-A.

FIG. 15B is a cross-section of FIG. 14A taken along line B-B.

FIG. 16 illustrates the bellows attached two a pair of pump assembliesconfigured to independently inflate each bellows.

FIG. 17 illustrates the knee bellows system inserted into a knee joint.

DETAILED DESCRIPTION

For the purposes of promoting an understanding of the principles of thepresent disclosure, reference will now be made to the embodimentsillustrated in the drawings, and specific language will be used todescribe the same. It will nevertheless be understood that no limitationof the scope of the disclosure is intended. In the following detaileddescription of the aspects of the invention, numerous specific detailsare set forth in order to provide a thorough understanding of thedisclosed embodiments. However, it will be obvious to one skilled in theart that the embodiments of this disclosure may be practiced withoutthese specific details. In other instances well known methods,procedures, components, and mechanisms have not been described in detailso as not to unnecessarily obscure aspects of the embodiments of theinvention.

Any alterations and further modifications to the described devices,instruments, methods, and any further application of the principles ofthe present disclosure are fully contemplated as would normally occur toone skilled in the art to which the disclosure relates. In particular,it is fully contemplated that the features, components, and/or stepsdescribed with respect to one embodiment may be combined with thefeatures, components, and/or steps described with respect to otherembodiments of the present disclosure. In addition, dimensions providedherein are for specific examples and it is contemplated that differentsizes, dimensions, and/or ratios may be utilized to implement theconcepts of the present disclosure. To avoid needless descriptiverepetition, one or more components or actions described in accordancewith one illustrative embodiment can be used or omitted as applicablefrom other illustrative embodiments. For the sake of brevity, thenumerous iterations of these combinations will not be describedseparately. For simplicity, in some instances the same reference numbersare used throughout the drawings to refer to the same or like parts.

Referring to FIG. 4A, a knee is shown with a tight ligament 102 and anopposing loose ligament 104 on opposite sides of the knee joint 101.Referring to the bone structure of the femur F and the tibia T, themedial condyle 105 is in contact with the tibial plateau while thelateral condyle 109 is spaced from the tibial plateau creating a void107. As shown in FIG. 4B, bone has been resected from both the femur Fand the tibia T and a trial implant guide has been positioned in theknee joint 101. As a result of the shortening of ligament 102 andresulting tension, in combination with the lengthening of ligament 104and resulting laxity, the femoral component 113 of the trial is angledat an initial angle A1 with respect to the tibial component 115.

Referring now to FIG. 4C, in accordance with the present disclosure, apartial epicondylar osteotomy is performed just superior of theattachment of the ligament 102 to the femur F. The osteotomy forms a gap110 having an initial width W. In one preferred form of the method, theinferior portion 120 the bone block 112 remains attached to the femursuch that the gap 110 defines a starting angle A2 with respect to theremainder of the femur. Force applied on the ligament 102 in thedirection of arrow A widens the gap 110 to form a second larger width Weffectively lengthening the ligament 102. As will be appreciated, forcein the direction of arrow A will also result in the bone block 112moving from a first angle A1 to a second position with an angle largerthan A1. The process of lengthening and checking for the proper lengthcan continue until the desired “effective” length of ligament 102 isreached. Often the length is increased until the knee joint is in abalanced position as shown in FIG. 7. It will be appreciated that thelength of ligament 102 does not actually increase, rather it is themovement of the underlying bone attachment 112 that results in an“effective” increase in the length of the ligament. Once the desiredwidth is achieved, a fixation member 130 may be positioned into thefemur through the bone fragment 112 attached to ligament 102 to maintainthe position of the fragment relative to the femur. As discussed furtherbelow, the fragment may be fixed by a screw, nail, cable or suture.

Referring to FIGS. 5A-5C, there is shown an epicondylar osteotomyfixation guide 150. The guide includes a blade 152 having a width W. Inone aspect, the width W is substantially the same as the width of anosteotome saw blade utilized to form the defect in the bone describedabove, while the thickness of the guide blade is substantially the sameas thickness of the saw blade. The guide blade 152 includes a passage154. Although shown as an oblong passage, it is contemplated that theblade may include openings through the blade or an indent in the bladeedge, provided a drill member can pass through at least a portion of theblade to form an opening in the bone. The guide includes a support arm156 which extends from the blade 152 and supports a tubular drill guide158 having an internal passage 160. The internal passage 160 has alongitudinal axis L5 that is aligned with the opening 154 in the blade.Drill guide 150 has inner face 161 that is configured for placementfacing the exterior of the femoral bone while the blade is configuredfor placement within a bone opening.

As shown in FIG. 6, the blade 152 of the drill guide 150 is positionedin the bone defect 110 such that the support arm holds the drill guide158 outside the femoral bone but under the skin 170 (shown in dashlines). In a preferred aspect, the drill guide has a relatively lowprofile so the skin and associated soft tissue can slide over the drillguide as the knee is moved through a range of motions. In one aspect, itwill be appreciated that a drill bit 171 may pass along the tubulardrill guide 158 and be guided into and through opening 154 alonglongitudinal axis L5.

In use, a saw or other instrument is used to create the bone defect orgap 110 while the knee is at approximately a 90 degree flexion position.The osteotomy starting point is at the junction of the distal articularsurface and the cortex directed superior. The inferior portion of thebone with the ligament attachment continues to be attached to the femur.Gradual distraction of the knee results in movement of the bone flap 112inferiorly toward the foot which acts to effectively lengthen theligament 102. A knee balancer, such as one available from Sultzer, isused to gauge accuracy of ligament balance and used as fulcrum forelongation of the partial epicondylar osteotomy proximal attached softtissues. The Sultzer balancer has a broad surface to decrease contactstress with the femur and tibia. It releases at a low maximum force thatprotects the cut surface of the tibia and femur from deformation.Continued distraction of the knee joint is applied until the desiredlengthening is achieved. Fixation of the epicondylar osteotomy once theextension gap is balanced is important to avoid posterior migration ofthe epicondyle that would affect the flexion gap. If epicondylarposterior displacement occurs it will affect rotation of the femoralprosthesis resulting in altered tracking of the patella femoral joint.

With the knee in flexion, the drill guide penetrating blade 152 ispositioned in the bone gap 110. The knee is then moved to extension tocheck ligament tightness. If additional adjustments are needed furtherdistraction can create additional effective length or slight closing ofthe gap can result in shortening. If the desired ligament length hasbeen achieved then the bone block 112 can be fixed in the finalposition. In one aspect of bone block fixation 112, the knee is extendedwhile the guide 150 stays in place. The guide is palpated through theskin to locate the guide barrel 158. An incision in skin S overlying thedrill guide 150 is formed to access the guide barrel 158. Once thedesire position has been achieved, a drill can be passed through thedrill guide to form an opening 164 in the bone block 112 and the femurF. As shown in FIG. 7, a fastener 180 such as a screw can be threadedinto the bone following opening 164 along axis L5 to maintain theposition of the bone block 112 relative to the femur F. Fixationpreserves the effectively lengthening of ligament 102 which allows theknee joint to rotate slightly to a balanced position where the femoralcomponent 113 of the trial is substantially parallel to the tibialcomponent 115 as illustrated by angle A1′ being substantially 0 degrees.

One sided exposure for fixation is an advantage however screw purchaseof cancellous bone is problematic in osteoporotic patients and a screwwithout a washer can easily migrate thru the epicondyle. A washer (notshown) can be utilized with the screw depicted in FIG. 7, but acts as asource to later weaken the ligament and also adds extra palpablematerial to a bony prominence. A special hook 196 (shown in FIG. 8) hasbeen designed to achieve fixation in a less prominent manner. It has theadvantage of more contact with the ligament bone junction to increasethe force necessary to pull through the osteotomy fragment. To place thehook, a tunnel is formed transversely through the femor and bone block,and a suture or cable 197 attached to the hook 196 is passed through thetunnel. The hook is attached to the bone block with attached ligament,the suture is tensioned and an anchor 198 engages the suture and theopposite side of the bone to maintain tension on the suture.

The balancing methodology has been described above for the varus kneebecause they are the most common knee deformity. The technique worksequally well with valgus knees in which the lateral epicondyle iselevated with maintenance of the anterior periosteum. On the lateralside balancing of the contracted tissues begins with elevation of thecontracted lateral capsule and IT band from the tibia. The posteriorcapsule is elevated from the posterior femur. Posterior femoral capsuleattachment and even elevation of the lateral gastroc is aided by alimited osteotomy of the posterior lateral femoral condyle duringextension gap balancing. Gradual distraction and fixation are performedthe same as the medial side.

Another factor that can be considered when balancing a severely deformedknee is that part of the ligament in-balance is related to theattenuation and laxity of the opposite ligaments and capsule of theknee's less worn side. Dealing with this problem by over lengthening theworn side will negatively affect knee kinematics.

To address the laxity of the ligament, a method has been developed inwhich a cable or suture is placed to balance the knee once the shortenedside has been returned to normal. This stabilizing cable or suture canalso be used to affect laxity patterns that are identified when a laxitypattern becomes apparent during trialing or after the implant issecured. The technique involves placement of the stabilizing suture orcable in the epicondyle to impart a tension force in flexion, extensionor both using the known center of the rotation of the specificprosthesis and point of laxity in flexion. Referring to FIGS. 9A and 9B,an elongated ligament tension element 206 is anchored to the femur atpoint 202 and to the tibia at point 204. In flexion as shown in FIG. 9A,the tension element 206 maintains a normal knee joint spacing 208between the femur and tibia. Similarly, when properly positioned andtensioned, the tension element 206 also maintains a normal knee jointspacing 210 in extension as shown in FIG. 9B. Circle 207 indicates aquadrant on the epicondyle for positioning of the tensioned ligamentaugmentation device to achieve the proper effect in both flexion andextension. With respect to FIG. 9A, the preferred position may be moreanterior and distal on the femur to achieve the proper tension inflexion. Conversely, as shown in FIG. 9B, the position of fixation forthe tensioned ligament augmentation device tends to be in a moreposterior and proximal quadrant of the epicondyle for the proper effectin extension. The knee can be manipulated and observed to evaluate theproper positioning of the tension member on the femoral epicondyle.

Referring to FIG. 10, the epicondylar anchor location is determined. Inone form, the femoral condyle may be imaged or exposed for visualinspection and anatomical landmarks used to identify the proper positionfor anchoring of the ligament support member. In another form, a guide230 secured to a femoral trial 220 or the implant itself may serve as anaccurate means to identify the anchoring point to assure the stabilizingcable or suture is tensioned most at the lax segment of the flexion arc.The guide 230 includes an attachment portion 232 for releasably engagingthe femoral trial 220 and an interconnected arm 233 that terminates in aguide tip 234. When positioned in the knee, the guide tip will engage orpoint to a location on the bone for drilling. As shown in FIG. 10, theguide tip may move slightly through a fixation area 236 as the knee ismoved from flexion to extension. Attachment of the cable or sutureshould occur in the attachment area 236, however there can be somemodification within the zone to account for specific knee movements. Forexample, if a laxity in extension is noted after the trial is placed theepicondylar fixation point is going to be more posterior and proximal onthe epicondyle. In contrast, if during deep flexion of the knee aportion of the ligament is particularly lax the epicondylar fixationpoint may be moved more anteriorly within the fixation area 236.

Referring to FIG. 11, the initial placement of a suture 140 in the kneeis shown. A bone tunnel 144 is formed in the femur based on the anchorattachment point determined as explained above. The inferior portion ofthe elongated ligament tension element 140, typically a suture or cable,is anchored to the tibia utilizing a bone anchor 142. Anchoring in thetibia at the level of the prosthesis stem base with a suture or cablefixation aid that penetrates the cortex and then flips perpendicular tothe cortex is a straight forward fixation method. In one form, the boneanchor 142 is an expandable anchor or flip anchor that can be deliveredin a minimally invasive reduced size configuration and then expandsafter positioning in the bone to an enlarged anchoring configuration asshown in FIG. 11. The ligament tension element 140 is positioned alonglax ligament 104′ and the superior portion is positioned in bone tunnel144. Passing suture superficial to the deep MCL or lateral capsule butdeep to the superficial MCL or lateral collateral is helpful. It is alsobeneficial to pass through the retinaculum to avoid impingement of themore superficial structures. In the illustrated embodiment, the sutureis passed through the bone fragment attached to ligament 102′ and may beused as a fixation element to hold the bone fragment in position.However, in a preferred embodiment illustrated in FIG. 11, the bonefragment is fixed separately and the bone tunnel 144 does not intersectthe bone fragment.

Referring to FIG. 13, although not limited to a specific design,additional details of a preferred elongated ligament tension element 140are shown. The tension element 140 is formed of a polyester material inthe form of a flattened strip or tape in the central area 170. Examplematerials include the FiberTape® and TigerTape available from Arthrexwhich are flattened polyester sutures with an ultra-high molecularweight polyethylene core. Although widths may vary, in one form thetapes are 2 mm wide tapes. The tapes provide broad compression andincreased tissue cut-through resistance compared to circular sutures. Inaddition to the use of suture tapes to limit pull through issues on bonetunnel 144, or as an alternative thereto, a cylindrical bone protectionferrule (not shown) may be placed at the entrance to bone tunnel 144 toinhibit suture pull through on the opening. Such ferrules have acylindrical body with a central passage to receive the suture and anenlarged head to engage the bone to inhibit migration. The transitionbetween head and the opening in the cylindrical body is rounded orchamfered to inhibit abrasion of the suture. In the embodimentillustrated in FIG. 13, the ligament tension member 140 is a compositeof a polyester suture tape 170 and a metallic cable 181. The tape 170 isjoined to the cable 181 by a coupler 176. The coupler has a series ofopenings 178 receiving a distal portion of the suture 174 and opening180 sized to pass the cable while retaining portion 182 joined to theproximal end of the cable. It will be appreciated that the proximal endof suture 172 is joined to a movable anchor 142 for tibial fixation. Thedistal end of the cable 145 may be fixed to the bone in any of a varietyof techniques know for cable to bone fixation.

Although it is contemplated that balancing of the knee can beaccomplished by simultaneously adjusting both the tight ligament and thelaxity on the opposing side of the knee, in practice, release of thetight ligament can be accomplished separately from tightening the laxityon the opposing side. Ligament tensioning is accomplished with anin-line tension device (not shown) attached to the cable end 145. Use ofa tension device, compared to manual pressure, allows more precisecontrol of the tension force being applied. In addition, the tensiondevice includes a force indicator measuring indicating the amount offorce being applied to the cable 144. In one aspect, the cable istensioned to between 15 and 30 lbs of force. The knee is moved throughone or more cycles through at least a part of the range of motionbetween flexion and extension while monitoring the force indicator. Ifforces above 30 lbs are indicated at any point along the range ofmotion, tension on the cable can be reduced by lengthening the ligamenttension element 140. Similarly, if tension on the cable falls below alower threshold, such as 15 lbs, then the ligament tension element 140can be shortened by the tension device to generate higher tension loads.It will be appreciated that the practice of adjusting the tension can berepeated as many times a necessary before committing to a cable orsuture length. This method also allows cycling of the knee to draw anycreep from the suture before the anchor is secured. In one preferredaspect, the target tension on the cable end 145 in the positions shownin FIGS. 9A and 9B is approximately 25 lbs of force.

As shown in FIG. 12, the ligament tension element 140 may be tensionedto achieve the desired knee balance such that femur condyle surface 160of the upper knee replacement component is maintained in closeapproximation or contact with the tibial component surface 162. Incomparing FIG. 11 to FIG. 12, the gap between these two surfaces isreduced by the application of tension to tension element 140 and theknee joint is more closely aligned from the unbalanced knee of FIG. 11to a balanced position as shown in FIG. 12. Once the desired alignmentand ligament balance has been achieved, tension on the ligament tensionelement 140 is maintained by securing the distal segment 145 to thedistal portion of the femur. In one form, an expandable anchor 146 issecured to the distal segment 145 and then moved to an anchoringconfiguration to maintain the position. In another form, an enlargedmember such as a washer is slid down the distal segment to engage thebone and a ferrule is crimped to the distal end 145 to maintain theposition of the cable relative to washer and thereby maintain forceagainst the bone. As discussed above, the location of the suture 140tunnel 144 through the femur is based on the center of rotation of theprosthesis as determined by a femoral trial positioned in the joint orby the actual prosthesis. Thus, the function of the knee can beoptimized by properly tensioning the ligaments. Also, if fine tuningadjustments need to be made after final placement of the prosthesis(both during the initial surgery or in a follow-up procedure), thesuture 140 can be loosened or tensioned as needed to achieve the desiredcorrection of ligaments 102′ or 104′, or both.

In another aspect of the present disclosure, a system 400 shown in FIGS.14-17 is provided to enhance equalization of the flexion and extensiongap. As will be explained in more detail below, the system 400 utilizesa pair of fluid filled bellows 420 and 440 to permit a virtuallyinfinite number of positions or heights to more accurately assess andmaintain the proper flexion and extension gap in the knee duringpreparation of the bone for receipt of an implant as well as balancingknee ligament tensions.

The extension gap for knee replacement procedures is determined by bonecuts of the femur and tibia. Cuts are made based on standing full lengthpre-op x-rays and may be refined based on data bank of knee alignmentand progression of disease. Bone cuts are made to restore mechanicalaxis to 0 degrees or within 2 degrees of neutral mechanical axis, butthe varus knee stays in up to 2 degrees of varus and any shift in valgusis avoided.

Currently the mechanical axis is checked by C-Arm, but navigation isanother alternative. Once cuts are made and checked the extension gap ismade rectangular by ligament releases. Rectangular gap shape andmillimeters of gap height are currently measured by a ratchetedbalancing device. The ratcheted devices have a disadvantage in recordingdisplacement and torque accurately. Ratcheted devices utilized havelarge (1.5 mm or 2 mm increment measured) of displacement and aresomewhat difficult to read. There is often a large jump in forcerequired to achieve the closest ratchet elevation needed toappropriately tension the ligaments. Therefore some discrepancies in gapbalancing are inherent.

The other problem is that the current ratcheted balancers cannot be usedas cutting guides or guides for cutting block pins. Therefore they areuseful only as a device to check gap equalization which is not efficientand requires multiple cuts in most situations. Deviations in flexion andextension gaps therefore can be at least 2 millimeters even when tryingto be as accurate as possible. Gap balancing is also more accurate whenthe patella is anterior which is impossible with distractors that arenot disassembled.

A bellows apparatus 400 has been designed to allow accurate assessmentof pressure and displacement. The extension gap is measured which allowsexact replication when completing the flexion gap. The bellows are fluidfilled and the fluid pressure as well as displacement is measured.Referring to FIG. 14A, a top view is shown with the upper plate 412illustrated with the inflation lumens 416 and 418 extending outwardlybeyond the perimeter of the upper plate. In FIG. 14B, a bottom viewshows the lower plate 414 with the inflation lumens 416 and 418extending outwardly beyond the perimeter of the bottom plate. Asillustrated, both inflation lumens extend from the same side of thebellows assembly 410. FIG. 15A is a cross section of FIG. 14A takenalong line A-A. Bellows 420 include corrugated sidewalls. In one form,the sidewalls include a series of rings 421 joined by a flexiblematerial forming a fluid tight chamber 430 that can expandlongitudinally along axis L4, but is constrained by the rings fromexpanding radially outwardly. In an alternative form, the sidewalls ofthe bellows are formed of a relatively stiff material that does notdistend under pressure but because of the folds 423 may expandlongitudinally along the axis L4. A central post 422 helps to maintainalignment as the bellows expand in the direction E from a first heightH1 to a second larger height. Referring now to FIG. 15B, this is across-section taken along line B-B of FIG. 14A. This view shows bellows440 along with the fill aperture 419 that is connected to inflationlumen 416 that are used to inflate fluid tight chamber 450. Bellows 420and 440 are constructed in the same manner.

Referring to FIG. 16, the bellows balancing system 410 is showninterconnected with the filling tubes 480 and 482. The filling tubes 480and 482 are connected to pumps 484 and 486, respectively. It will beappreciated that movement of handles 488 and 490 via rotation willgenerate fluid pressure in the system that can be displayed by pressuregauge 492 and 494, respectively. Each of the bellows is inflatedindependently permitting precise changes in angles and pressures toachieve the proper balance of the knee joint. Typically the bellows areutilized before cuts are made so the bellows provides a guide for theproper amount of bone removal needed to proper fit the knee replacementimplant. Referring to FIG. 17, the bellows balancing system 410 isplaced in the knee joint before expansion and then expanded in situuntil the desired height and/or pressure is achieved.

If a subtle difference exists in extension gap symmetry, it can beidentified by the bellows. Modification of the femoral cut can be usedby securing a cutting guide based on the platform of the bellowsapparatus 410. The refinement in the bone cut is made only if themechanical axis following the correction is felt to be acceptable. Inthis manner a perfect symmetrical extension gap is accomplished to alloweasy duplication in flexion. Factors such as limb position, limbsupport, tibia rotation, patella position, optimal ligament cycling andtension response and effect of PCL partial release can be studiedaccurately.

Additional details of the bellows apparatus 400 is set forth in FIGS. 16and 17. As described above, each syringe can provide a range ofexpansion force up to 25 lbs., although additional force up to about 40lbs. could be generated by larger syringes if desired. Further, althoughdual bellows are disclosed in the present embodiment to provide greatervariability between lateral aspects of the knee, it is contemplated thata single bellows can be provided to achieve desired gap refinement.Also, an index (ruler) may be attached to the anterior surface of thebellows to provide a measurement off the bellows to allow the drillingof holes for placement of jigs to guide making cuts in the bone.

The above devices and methods have been described in the context of anopen surgical technique that is manually implemented. It is contemplatedthat one or more aspects of the technique can be implemented by arobotic surgical system configured for knee surgeries such as thatdescribed in US2009/0000626 entitled “Haptic Guidance System andMethod,” incorporated herein by reference in its entirety.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions andalterations herein without departing from the spirit and scope of thepresent disclosure. Furthermore, although elements of the describedembodiments may be described or claimed in the singular, the plural iscontemplated unless limitation to the singular is explicitly stated.Additionally, all or a portion of any aspect and/or embodiment may beutilized with all or a portion of any other aspect and/or embodiment.

What is claimed is:
 1. A system for load balancing in knee replacementprocedures, the system comprising: a ligament release portion includingan epicondylar osteotomy fixation guide and an epicondylar osteotomyfixation member; and a ligament tension portion including an elongatedligament tension element having a first anchoring element disposed nearan inferior end and configured for anchoring below the knee joint, and afemoral anchoring portion for movably anchoring the elongated ligamenttension element to the femur.
 2. The system of claim 1, wherein theepicondylar osteotomy fixation guide includes a penetrating bladedefining an aperture therethrough, the aperture extending in the medialto lateral orientation when the penetrating blade is positioned in anepicondylar osteotomy, the fixation guide further including a drillguide joined to the penetrating blade by a support arm, the drill guidehaving a passage with a guide axis, the support arm aligning the guideaxis with the aperture.
 3. The system of claim 1, wherein the supportarm has a length sufficient between the penetrating blade and the drillguide to space a proximal end of the drill guide outside of soft tissueoverlying the epicondylar osteotomy when the knee is in extension. 4.The system of claim 1, further including an epicondylar osteotomy sawblade for forming the osteotomy, saw blade having a width and athickness and wherein the penetrating blade has a blade width and ablade thickness substantially matching the saw blade width andthickness.
 5. The system of claim 1, wherein the penetrating blade has aretention means for engaging the bone inside the osteotomy to maintainthe penetrating blade in the correct position.
 6. The system of claim 1,wherein the epicondylar osteotomy fixation member comprises a screw. 7.The system of claim 1, wherein the epicondylar osteotomy fixation membercomprises a bone anchor configured to engage an epicondylar osteotomybone flap and a flexible elongate element to join the bone anchor to thefemur.
 8. The system of claim 1, further including a knee replacementsystem with a femoral component and a tibial component.
 9. The system ofclaim 1, wherein the elongate ligament tension element includes alongitudinal ligament functional replacement portion configured forextending along the existing knee ligament and a transverse tensioningportion configured for extending transversely through the femur.
 10. Thesystem of claim 9, further including a coupling member joining thelongitudinal functional ligament replacement portion to the transversetensioning portion.
 11. The system of claim 9, wherein at least thelongitudinal functional ligament replacement comprises a polyestermaterial.
 12. The system of claim 11, wherein the longitudinalfunctional ligament replacement comprises a flattened portion.
 13. Thesystem of claim 9, wherein the transverse tensioning portion comprises acable.
 14. The system of claim 9, further including a tensioning memberconfigured to engage at least a portion of the transverse tensioningportion, the tensioning member configured to pull the tensioning portionthereby generating a tension in the connected longitudinal functionalligament replacement.
 15. The system of claim 14, wherein the tensioningmember can generate at least 15 pounds of tension in the longitudinalfunctional ligament replacement.
 16. The system of claim 8, furtherincluding a guide for forming a passage in the femur, guide having aninferior portion for engaging at least a portion of the knee replacementsystem and a superior portion defining a drill guide.
 17. A method forload balancing in knee replacement procedures, the method comprising:evaluating ligament balance in a knee; identifying a loose ligament thatis too lax to properly function to support the knee after insertion of aknee replacement device; anchoring an inferior end portion of anelongate ligament support member below the knee; extending the elongateligament support member along the loose ligament; evaluating tension ofthe elongate ligament support member in at least one of flexion andextension of the knee to determine the appropriate tension on theelongate ligament support member; and fixing a superior portion of theelongate ligament support member to the femur to maintain theappropriate tension.
 18. The method of claim 17, further including:forming a passage through the femur; passing a superior portion of theelongate ligament support member through the passage from the ligamentside to the anchor side; and apply tension to the superior portion ofthe elongate ligament support member adjacent the anchor side to therebytension the member on the ligament side.
 19. A knee load balancinginstrument, comprising: a first bellows having a first upper boneengaging end plate and a first lower bone engaging endplate and a firstmovable sidewall joining the first upper and lower bone engaging platesalong a longitudinal axis, the first movable sidewall formed ofcorrugated material inhibiting outward expansion permitting longitudinalexpansion, the first upper and lower bone engaging plates along with thefirst movable sidewall joined to form a fluid tight first fluid chamber;a second bellows having a second upper bone engage end plate and asecond lower bone engaging endplate and a second movable sidewalljoining the second upper and lower bone engaging plates along thelongitudinal axis, the second movable sidewall formed of ringsinhibiting outward expansion and flexible material positionedlongitudinally between the rings to permit longitudinal expansion, thesecond upper and lower bone engaging plates along with the secondmovable sidewall joined to form a fluid tight second fluid chamber; afirst tube joined to the first fluid chamber and configured forconnection a first pump; and a second tube joined to the second fluidchamber and configured for connection a second pump, wherein the firstfluid chamber and associated first movable sidewall is movablelongitudinally independently from the second fluid chamber and secondmovable sidewall.